I have been excited about the new 7.3 engine since I heard about it. As I learned more about it, I have become concerned that apart from variable valve timing, there appears to be very little difference between it and the 460 gas engine of the 1990's. Both had port EFI injection, push rod engines, about the same displacement. So my big concern is that this thing is going to suck gas like crazy. If they had direct injected it like chevy has the 6.6 they would have gotten some serious numbers with some reasonable economy, and of course all the headaches that go along with direct injection. Carbon build up on the intakes etc etc. Even with the 10 speed which might help it might not add that much. The guys getting 14 mpg out of their 6.2 with 4.30 gears are getting the same mpg as I am getting with my V10 with 4.30 gears and a 5 speed torqshift empty at 65 mph. I am hoping someone can give me some enlightenment on the reason this 7.3 won't be a gas hog. I sure hope that Ford got the spark plugs right on this one.

 

At this point everything is speculation, my understanding from attending the work truck show in Indiana is the 7.3 is going to be a dedicated heavy vocational engine. It has a higher duty cycle than the 6.2. This engine isn't geared towards fuel economy, its geared for heavy use in areas where the diesel isn't cost effective. It's all about margins for fleets. If the engine gets 5mpg at max 35k GCWR in a F-750 and the lifespan pushes 150k then it's a win for fleet operators. Currently same configuration with the 6.8 is netting 4mpg and failures start showing around 100k.

 

Now that does make sense!

 

The engineer giving the presentation emphasized the fact that the 7.3 was designed to run at the ideal fuel air mixture (stoichiometric ratio) and that this would produce the best fuel economy and cleanest emission under the loaded conditions that it is designed for. I would expect poor fuel economy when not loaded just due to the large displacement. My truck is towing about 90% of the time so unloaded fuel economy isn't a priority. I get 8.5 mpg towing 10K with my 6.2/3.73 - I hope the 7.3 would get at least 8.0 mpg with the same load.

 

I have 2018 F250 diesel(1st one for me) I use to tow my 27' travel trailer and commute. I bought this because in my opinion the 6.2 would not satisfy my towing needs(this is not a discussion if the 6.2 could or could not). I can pull my trailer up any hill faster than any sane person should. I've never had a vehicle tow as well as this diesel. If the 7.3 turns out to be a bridge between the 6.2 and the 6.7 by more than a little, the diesel will go and the 7.3 will replace it.

 

Now that makes really good sense....
I did read within this topic that the 6.2l would also be available with a 10 speed at a higher trim level.
Yet do not see any discussion on this So was I mistaken?
Certainly would help with MPGs for us towing <12k on an irregular basis and do not need the beast of a 6.7l.

 

Direct injection can be more efficient, but it's just not that much of a difference. I asked this same question to Mike Harrison almost 10 years ago when we were discussing the 6.2 L engine that was about to be released. Mike was the chief engineer for the project, and here was his remark on direct injection:

https://www.ford-trucks.com/forums/9...as-engine.html

Another great example is the Toyota Prius, which is been the most fuel-efficient thing on the road for almost 20 years now. It's always had poor injection, and is significantly more efficient than just about everything direct injected on the market, which includes smaller cars with less power. Direct injection is great, but not significantly more efficient than port injection.

 

I'm actually happy it's not DI. The problems and maintenance associated with DI on a tow vehicle is not worth the gains. I think simple is good when it comes to reliability.

 

The Prius is an apples-to-oranges comparison, it is a hybrid and the engine isn't running all the time. I figure Toyota went with port injection to keep the costs down. Most all other Toyotas are DI. In fact, there are fewer and fewer port injection engines around each year from all manufacturers. I think Ford went with port on the 7.3 for costs and also because it's not necessary in its intended applications yet.

Can't help but notice Ford seems to be having more problems with DI than other manufacturers too............

 

When looking at big V8 fuel economy it might be more helpful to look at the amount of work (e.g. payload or trailer weight) being done per gallon of fuel.

For instance, a prius may get 54 mpg but how many trips will it take to move 4000 pounds of payload or 15,000 lbs of trailer weight? In other words, mile per gallon is not the final number when selecting a vehicle....a person needs to consider what's being done per gallon.

It's kinda weird to hear a 7.3 liter engine being called a gas hog...the stoichiometric air to fuel mix is the same for a 7.3 as it is for what ever engine is in a prius. The 7.3 is just bigger because it's meant for a bigger job.

 

My point was about engine efficiency, not trying to equate a Prius engine with its exact polar opposite. But on the highway that Prius engine runs 100% of the time, as it cannot shut off below 45 mph, and they still consistently see nearly 50 mpg. Which is something that other gas powered cars just can’t do, even with DI.

More relevant to the conversation was my quote from Mike Harrison above, who insisted in 2009 there was only 1-2% efficiency increase they could be gained from DI.

 

Not sure how much of the Prius mpg is due to engine efficiency. Properly configured Saturns from 20 years ago got mid to high 40's their whole life. They had barely enough power to get out of their own way but got excellent mpg in a 5 passenger car with respectable trunk space.

Nice thing about today's cars is engines can be made smaller with enough power to cruise but also have good top end power for passing when needed thanks to variable timed cams and more efficient trannies.

I think the 7.3 is aimed at a steady diet of heavier loads and trailers. For higher mpg in lightly used trucks the 6.2 or the F150 is there.

 

VW also having alot of issues..common thread is turbo applications. Can't run an intake and valve cleaner to remove carbon buildup due to turbos. Design on the larger Ford engines (2.7, 3.5) seem to do better due to how the deliver the fuel and the intake designs. As more auto makers use DI and Turbos we will see more until the figure it out.

 

When Ford went from the 5.4 to the 6.2 in the Super Duty I don't believe fuel economy got any worse. I don't expect much to change with the new 7.3.

 

It's hard to get a great comparison because they are rated for fuel efficiency and heavy duty pickups.

But both engines were offered in the F150, and the 6.2l was rated as less efficient in that platform: